1. Field of the Invention
The present invention relates to an imaging device for use in a digital camera having a battery charging function and a data transfer function, and to a control method therefor, and program for the imaging device.
2. Description of the Related Art
In recent years, the number of products which make use of the DLNA (Digital Living Network Alliance) standard for connecting electronic products and everyday electronic appliances to one another over a network has been increasing. Moreover, it is predicted that electronic apparatus in the home will become increasingly networked. Connection via a network allows the electronic apparatus to transfer data. For example, moving picture data captured by a digital video camera can be easily transferred to a hard disk recorder by simply connecting the digital video camera to the network.
Also, the storage capacity of storage media used in electronic apparatus is increasing extremely quickly. As a result, it is now possible to record high quality images and moving pictures onto storage media for long periods. When a storage medium is capable of repeatedly recording moving picture data or image data in this way, the captured image data must be periodically transferred to an external device. However, when the amount of data is large, the data transfer takes time.
Also, if the electronic apparatus is a portable digital camera, charge is also necessary since most cameras are battery driven. Generally, when the battery is being charged, portable cameras are constrained by the inability to perform other operations because built-in power supply circuits stop supplying power to power consuming units other than the charging circuit.
To solve the above-described problem, a technique by which current supplied from a data transfer bus is used to simultaneously charge the battery and transfer data has been proposed (see, for instance, Japanese Laid-Open Patent Publication (Kokai) No. 2002-237971).
However, in conventional cameras, battery charge and data transfer after use take a long time to complete. Hence the problem exists that the camera cannot be used for long periods while the battery charge and data transfer are taking place.
Also, when there is only a limited amount of time before the camera is to be reused, it may be the case that only one of the battery charge and the data transfer is possible. This means that the camera may have insufficient storage space or run out of battery when next used.
Moreover, it is the user who has to switch a camera operation unit between the batter charge and the data transfer. Hence, the user is obliged to monitor the amount of charge remaining in the battery and the available storage capacity in the storage medium. This is complicated and time consuming.
Hence, a way of automatically charging the battery and performing data transfer as appropriate in the limited period of time before the camera is next used is needed for when the battery charge and data transfer cannot be fully completed.
According to the above-described Japanese Laid-Open Patent Publication (Kokai) No. 2002-237971, the battery charge and data transfer can be performed simultaneously, and it is therefore possible to shorten the total period required for battery charge and data transfer. However, since the method of the Japanese Laid-Open Patent Publication (Kokai) No. 2002-237971 cannot be realized without a connection unit that includes a power supply function such as the USB (Universal Serial Bus) of a personal computer, connection using the method for connecting the electronic apparatus to the network is not necessarily possible. Also, since the construction of the power circuit is complex, an increase in the number of parts and a rise in cost are unavoidable.